Underwater cameras are usually contained, whilst underwater in a waterproof housing to which a lens port is attached. The housing must be able to be connected to by a number of differing lens ports in the same way as a camera is able to receive a number of differing lenses. Thus the connection between the housing and the lens port must be temporary in nature but, as leakage can cause severe damage to the camera and the lens inside the housing, also be securely sealed. “O” rings are commonly used for this purpose.
Often a threaded connection is used but this method has the disadvantage that there is no indication to inform the user when to stop tightening the port. This often results in over-tightening, which makes it difficult to remove the port from the housing.
Further some ports carry external knobs for the operation of the zoom and/or focus rings of the lens and the user needs to ensure that these knobs are in the position where the user finds them comfortable and convenient to use once the port is connected to the housing. To change the position of the knobs the relative position of the external threads and knobs must be changed. This can be achieved by loosening and relocating the screws on the lens port. However there may be upwards of sixteen such screws to undone relocate and re-tighten which makes the procedure time consuming.
In another form of connection bayonet tabs are used, there being for example three such tabs which pass through recesses in the front of the housing before the user rotates the port relative to the housing. This gives only limited choice of the position of the knobs. Also the friction between the port and housing is high due to the existence of the “O” ring, and therefore the lens port is difficult to turn, making insertion and removal of the lens port to and from the housing also difficult.
In a still further existing construction a pair of plastic clamps, 180 degrees apart are used as locking devices. Each plastic clamp contains a slot in which a screw is fitted to allow movement of the clamps in the direction parallel to the slot. The port can be inserted into the housing while the clamps are in an outward position, and the port then fixed into position by moving the clamps inwardly. The port is then securely locked to the housing as the port can only be removed by pulling out safety handles on the clamps and then moving the clamps outwardly. Although this method of locking the port to the housing does not require the user to turn the port relative to the housing the locking devices are situated outside the housing and are therefore more prone to damage, for example, by physical impact, when compared to other locking methods.